The present invention relates to drive mechanisms for plungers of balers for making parallelepiped bales, and more particularly, relates to hydraulically powered plunger drives.
It is common baling practice to use a reciprocating plunger to compact charges of cut vegetation within a baling chamber. Reciprocation of the plunger is usually effected either by a tractor power take-off driven mechanism including a rotating crank coupled to the plunger by a connecting rod, or by a hydraulic cylinder having its piston rod coupled directly to the plunger. An example of a typical power take-off driven mechanism is illustrated in U.S. Pat. No. 4,524,574, issued Jun. 25, 1985, while an example of a typical hydraulically driven plunger is illustrated in U.S. Pat. No. 4,202,262, issued May 13, 1980.
The simplicity of using a hydraulic piston and cylinder unit (hydraulic actuator), as shown in the above-identified patent, for driving a plunger is desirable, but this structure has the drawback of requiring a hydraulic actuator of substantial length in order to produce the desired travel of the plunger and of requiring a hydraulic pump having a displacement chosen for supplying the volume of fluid necessary for stroking the plunger drive actuator at the speed required for baling operation.